Polishing method by blasting and nozzle structure for a blasting apparatus for use in the polishing method

ABSTRACT

In a polishing performed by imparting kinetic energy to abrasive using a compressed gas flow, horizontal cutting force is obtained while vertical cutting force acting on a surface of a workpiece is inhibited. A compressed gas containing no abrasive is ejected from an accelerated flow generation nozzle  10  toward a surface of a workpiece W to generate an accelerated flow S along the surface of the workpiece W. Also, abrasive  30  is introduced into an abrasive introduction path  20  opening toward the surface of the workpiece W at an area where the accelerated flow S is generated, preferably together with a compressed gas to merge the abrasive  30  with the accelerated flow S and make the abrasive  30  slide along the surface of the workpiece W. Thus, horizontal cutting force is exerted on the surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing method by blasting and a nozzle structure for a blasting apparatus for realizing the polishing method. More specifically, the present invention relates to a workpiece polishing method which is performed by imparting kinetic energy to abrasive using a compressed gas flow and to a structure of a nozzle portion of a blasting apparatus for realizing the polishing method using the blasting apparatus.

2. Description of the Related Art

Conventional known polishing methods for improving the flatness, i.e., so-called “surface roughness” of a surface of a workpiece and processing the surface into a smooth surface such as a mirror surface include, for example, polishing using polishing paper or polishing cloth, polishing using a buff, lapping, polishing by contact with rotating abrasive grains, superfinishing in which polishing is performed on a workpiece by contact with abrasive grains given ultrasonic vibration, and the like.

On the other hand, blasting in which abrasive is ejected to a surface of a workpiece together with a compressed fluid, e.g., compressed air, to perform cutting is generally not used as polishing processing for improving the flatness of a surface of a workpiece, though blasting is a process relating to a processing technique also using abrasive.

In this process, abrasive ejected together with a compressed gas or the like is collided with a surface of a workpiece by blasting, and the surface of the workpiece is processed using the collision energy. Accordingly, the abrasive exerts cutting force on the surface of the workpiece W in the vertical (depth) direction. As a result, as shown in FIG. 18, cutting proceeds while morphological characteristics of irregularities originally existing on the surface of the workpiece are being inherited. Thus, surface planarization is difficult to achieve despite a large amount of cutting.

Moreover, in blasting, cutting is performed using the collision energy of abrasive as described previously. Accordingly, planarization is also made difficult by the fact that irregularities are newly formed on the surface of the workpiece due to cutting and deformation associated with the collision of abrasive grains and that the surface of the workpiece is thus changed into a satin finished surface.

As described above, in conventional general blasting methods, it is difficult to planarize a surface of a workpiece, and particularly to perform planarization with high precision to obtain a surface such as a mirror surface. Conventionally, there has also been proposed a technique for eliminating such disadvantages of blasting, and inhibiting a satin finished surface from being produced on a surface of a workpiece to enable the surface to be processed into a plane surface, e.g., a mirror surface, by blasting.

As one example of such blasting methods, the applicant has proposed a technique for inhibiting a satin finished surface from being produced by ejecting or projecting abrasive having a structure in which abrasive grains are dispersed in a base material which is an elastic body (in this specification, abrasive having such structure is referred to as “elastic abrasive”) onto a surface of a workpiece at a predetermined angle of incidence to cause the collision energy to be absorbed by the plastic deformation of the elastic body, and for enabling blasting to be used for the improvement of flatness by causing the elastic abrasive to slide along the surface to be processed (Japanese Unexamined Patent Application, Publication No. 2006-159402).

Moreover, the applicant has also proposed a technique for improving flatness by generating an ejection flow of abrasive along a surface of a workpiece even in the case where existing abrasive (abrasive grains) is used and where the abrasive is ejected together with a compressed fluid to the surface of the workpiece to be processed under the following conditions:

0<V·sinθ≦½·V

(V=the speed of the abrasive in the ejection direction, θ=the angle of incidence of the abrasive with respect to the surface of the workpiece to be processed) (Japanese Unexamined Patent Application, Publication No. 2005-022015).

Of the above-described conventional polishing methods, polishing using polishing cloth or polishing paper, lapping, polishing using a grinding wheel and the like must include multiple polishing steps in which the particle diameter of abrasive is gradually decreased because abrasive having a small particle diameter exerts only a weak polishing force. Thus, work becomes complicated.

Moreover, the amount of polishing depends on processing pressure. However, if processing pressure is set low to avoid the excessive occurrence of processing strains, processing speed decreases, and productivity becomes low.

On the other hand, in the case where a high processing pressure is applied, a grinding crack or polishing crack may occur.

Moreover, as described previously, processing strains occur in a surface layer of a workpiece undergoing polishing with processing pressure applied thereto.

Accordingly, in the case where the workpiece is, for example, a silicon wafer, the processing strains occurring in polishing processing may need to be removed in order to secure a perfect crystal layer near the surface of the wafer. Accordingly, a step of heat-treating the wafer which has undergone polishing, removing the surface layer using an agent such as an acid or an alkali, or the like needs to be performed after the polishing processing. Moreover, in the case where the surface layer is removed using an agent such as an acid or an alkali, work therefor is very complicated for reasons such as the necessity of appropriately treating liquid waste of the agent such as an acid or an alkali used at that time.

On the other hand, in the methods disclosed in the aforementioned documents '402 and '015, compared to polishing methods such as lapping which have been conventionally generally performed, excess stresses are less prone to occur in a workpiece after polishing. Moreover, strains and the like are less prone to occur after processing.

However, in the blasting method of the aforementioned document '402, to prevent a satin finished surface from being produced on a surface of a workpiece and cause abrasive to slide along the surface of the workpiece, the aforementioned elastic abrasive is used to cause the plastic deformation of the elastic abrasive to absorb the collision energy. Thus, the use of abrasive having a special structure is required.

In the blasting method introduced as the aforementioned document '015, by appropriately setting ejection conditions of abrasive, abrasive can be made to slide along a surface of a workpiece even in the case where general abrasive (abrasive grains) is used rather than using special abrasive. Thus, a polishing process can be relatively easily performed by blasting.

However, in this method, the horizontal component of force acting on a surface of a workpiece in the collision of abrasive is set sufficiently larger than the vertical component of the force to prevent collided abrasive grains from producing a satin finished surface on the surface of the workpiece. Unless the angle of incidence θ is set to zero, the vertical component cannot be removed.

Moreover, when an attempt to reduce the angle of incidence θ close to zero is made in order to reduce the aforementioned vertical component, it is necessary to perform ejection with an ejection nozzle inclined with respect to the surface of the workpiece, or to use an auxiliary device or the like for guiding an ejection flow ejected from an ejection nozzle to a flow along the surface of the workpiece (see FIGS. 3 to 13 of the aforementioned document '402). Thus, this method may be difficult to apply in some cases, depending on the workpiece shape or the like.

It should be noted that in the above description, flatness improvement (smoothing) has been mainly described as one example of the “polishing” of a workpiece. However, as well as flatness improvement (smoothing), in other polishing works such as the work of reducing the smoothness of (roughening) an original surface and the work of removing a coating provided on a surface, enabling polishing to be performed by relatively simple work similar to that in blasting in a state in which vertical cutting force is inhibited has the following advantages: damage to the workpiece can be reduced; the amount of cutting can be inhibited from increasing more than necessary; and the like.

Accordingly, the present invention has been made to eliminate the disadvantages of the above-described conventional techniques. In the present invention, polishing is performed by imparting kinetic energy to abrasive using a compressed gas flow as in the known blasting methods. However, an object of the invention of the present application is to provide a polishing method in which the improvement of flatness of a surface of a workpiece, other adjustments of surface roughness, cutting and removal of a surface portion such as the removal of a surface coating, and other various kinds of polishing can be performed by inhibiting vertical cutting force acting on the surface of the workpiece from occurring and causing horizontal cutting force to be exerted even in the case where general abrasive (abrasive grains) is used rather than using abrasive having a special structure such as elastic abrasive, and to provide a nozzle structure for a blasting apparatus for use in the polishing method.

SUMMARY OF THE INVENTION

To achieve the above-described object, a polishing method by blasting of the present invention comprises the steps of introducing a fluid jet P1 which is a compressed gas containing no abrasive, into an accelerated flow generation nozzle 10 arranged to be pointed at a surface of a workpiece W and ejecting the compressed gas to generate an accelerated flow S along the surface of the workpiece W by the ejection, and

introducing abrasive 30 into an abrasive introduction path 20 opening toward the surface of the workpiece W at an area where the accelerated flow S is generated to merge the abrasive 30 with the accelerated flow S and make the abrasive 30 slide along the surface of the workpiece W.

In the above-described polishing method, the abrasive 30 may be mixed with a carrier fluid P2 which is a compressed gas at a pressure lower than the pressure of the ejection fluid P1 introduced into the accelerated flow generation nozzle 10, e.g., a pressure which is two-thirds or less of the pressure of the ejection fluid P1, to be introduced into the abrasive introduction path 20.

Moreover, to realize the polishing method, a nozzle structure for a blasting apparatus (blast nozzle 1) of the present invention comprises an accelerated flow generation nozzle 10 for ejecting a compressed gas containing no abrasive supplied as an ejection fluid P1 from a compressed gas supply source (not shown) toward the surface of the workpiece W to generate an accelerated flow S along the surface of the workpiece W, and

an abrasive introduction path 20 opening toward the surface of the workpiece W at an area where the accelerated flow S is generated, and having the abrasive 30 from an abrasive supply source (not shown) supplied thereto.

The arrangement of the accelerated flow generation nozzle 10 and the abrasive introduction path 20 in the above-described nozzle structure can be realized by arranging an end portion of the accelerated flow generation nozzle 10 on the ejection orifice 11 side in the abrasive introduction path 20 (see FIGS. 1 to 3).

Instead of the above-described configuration, a configuration may be employed in which the ejection orifice 11 of the accelerated flow generation nozzle 10 is formed into the form of a slit and in which an opening 21 of the abrasive introduction path 20 is arranged parallel to the ejection orifice 11 (see FIGS. 4A and 4B). In this case, further, the opening 21 of the abrasive introduction path 20 may be arranged on each of opposite sides of the ejection orifice 11 of the accelerated flow generation nozzle 10 (see FIGS. 5A and 5B).

Further, it is preferable that the gap δ1 between the ejection orifice 11 of the accelerated flow generation nozzle 10 and the surface of the workpiece W is set to, for example, 0.5 to 3.0 mm, and that the gap (δ1+δ2) between the opening 21 of the abrasive introduction path 20 and the surface of the workpiece W is made wider than the gap M between the ejection orifice 11 of the accelerated flow generation nozzle 10 and the surface of the workpiece W by, for example, approximately 1.0 to 3.0 mm (see FIG. 3).

With the above-described configuration of the present invention, the polishing method of the present invention has the following significant effects.

The ejection of the ejection fluid P1 to the surface of the workpiece W and the introduction of the abrasive 30 are performed through separately provided routes, i.e., the accelerated flow generation nozzle 10 and the abrasive introduction path 20, respectively. Thus, after the accelerated flow S along the surface to be processed of the workpiece W is generated, the abrasive 30 is merged with the accelerated flow S. This enables the abrasive 30 to slide along the surface of the workpiece W together with the accelerated flow S without colliding against the surface of the workpiece in the vertical direction.

As a result, cutting force acting on the surface of the workpiece W in the vertical direction can be inhibited from occurring, and horizontal cutting force can be generated by the sliding of the abrasive 30. Accordingly, damage to the workpiece W can be greatly reduced during polishing, and a polishing method can be provided which can be applied to polishing for flatness improvement (smoothing) or the like, which has been difficult in conventional general blasting.

In particular, the carrying of the abrasive 30 is performed using a mixture fluid of the abrasive 30 and the carrier fluid P2 at a pressure lower than the pressure of the ejection fluid P1, preferably the carrier fluid P2 at a pressure which is two-thirds or less of the pressure of the ejection fluid P1. This makes it possible to smoothly introduce the abrasive 30 while greatly inhibiting the abrasive 30 from exerting vertical cutting force on the surface of the workpiece W. Also, the carrier fluid P2 discharged from the opening 21 of the abrasive introduction path 20 toward the accelerated flow S acts to press the accelerated flow S toward the surface of the workpiece W. Accordingly, the accelerated flow S can be prevented from being separated from the surface of the workpiece W, and the followability of the accelerated flow S to the surface of the workpiece W can be improved.

Further, by setting the gap (δ1+δ2) between the opening 21 of the abrasive introduction path 20 and the surface of the workpiece W wider than the gap M between the ejection orifice 11 of the accelerated flow generation nozzle 10 and the surface of the workpiece W, preferably by setting the gap δ1 to 0.5 to 3.0 mm and setting the gap δ2 to 1.0 to 3.0 mm, the ejection fluid P1 ejected from the accelerated flow generation nozzle 10 becomes the accelerated flow S, which is a flow favorably running along the surface of the workpiece W when passing through the gap δ1, and is introduced into the gap (δ1+δ2) between the abrasive introduction path 20 and the surface of the workpiece W which is formed wider than the gap δ1. Thus, the accelerated flow S is not interrupted by the existence of the abrasive introduction path 20, and the accelerated flow S and the abrasive 30 can be favorably merged at this position.

It should be noted that the above-described method can be realized by a nozzle structure for a blasting apparatus comprising the accelerated flow generation nozzle 10 for ejecting a compressed gas supplied as an ejection fluid P1 from the compressed gas supply source (not shown) toward the surface of the workpiece W to generate the accelerated flow S along the surface of the workpiece W, and the abrasive introduction path 20 opening toward the surface of the workpiece W at an area where the accelerated flow S is generated and having the abrasive 30 from the abrasive supply source (not shown) supplied thereto.

In the nozzle structure having a configuration in which the abrasive introduction path 20 is made to communicate with the abrasive supply source (not shown) for supplying the abrasive 30 as a mixture fluid with the carrier fluid P2 which is a compressed gas, the carrying and merging of the abrasive 30 can be smoothly performed. Also, as described previously, since the carrier fluid presses the accelerated flow S toward the surface of the workpiece, the accelerated flow S can be favorably prevented from being separated from the surface.

Further, in a configuration (see FIGS. 1 to 3) in which an end portion of the accelerated flow generation nozzle 10 on the ejection orifice 11 side is arranged in the abrasive introduction path 20, the abrasive 30 can be made to slide along the surface of the workpiece W around the entire circumference of the ejection orifice 11 of the accelerated flow generation nozzle 10. Thus, the processing area can be widened.

Moreover, in a configuration (see FIGS. 4A, 4B, 5A and 5B) in which the ejection orifice 11 of the accelerated flow generation nozzle 10 is in the form of a slit, polishing processing can be performed simultaneously over a wide area corresponding to the length of the slit. In particular, in a configuration (see FIGS. 5A and 5B) in which the opening 21 of the abrasive introduction path 20 is provided on each of opposite sides of the ejection orifice 11 of the accelerated flow generation nozzle 10, polishing processing can be performed simultaneously in two opposite directions along the width of the opening of the nozzle 10 from the accelerated flow generation nozzle 10 as a center. Thus, efficient processing can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the invention will become understood from the following detailed description of preferred embodiments thereof in connection with the accompanying drawings in which like numerals designate like elements, and in which:

FIG. 1 is a schematic cross-sectional view showing a configuration example of a nozzle structure (blast nozzle) for use in a polishing method of the present invention;

FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of a tip portion of the blast nozzle;

FIGS. 4A and 4B are explanatory diagrams showing a modified example of the tip portion of the blast nozzle. FIG. 4A is a side cross-sectional view, and FIG. 4B is a cross-sectional view taken along line B-B of FIG. 4A;

FIGS. 5A and 5B are explanatory diagrams showing a modified example of the tip portion of the blast nozzle. FIG. 5A is a side cross-sectional view, and FIG. 5B is a cross-sectional view taken along line B-B of FIG. 5A;

FIG. 6 is an explanatory diagram schematically showing the process of cutting a surface of a workpiece by the method of the present invention;

FIG. 7 is a diagram for explaining RMS (root mean square roughness);

FIGS. 8A and 8B are electron micrographs of a surface of an unprocessed test piece (soda glass: minor surface). FIG. 8A is a planar image, and FIG. 8B is a stereoscopic image;

FIGS. 9A and 9B are electron micrographs of a surface of soda glass processed by the method (Example 1) of the present invention. FIG. 9A is a planar image, and FIG. 9B is a stereoscopic image;

FIGS. 10A and 10B are electron micrographs of a surface of soda glass processed by known blasting (Comparative Example 1). FIG. 10A is a planar image, and FIG. 10B is a stereoscopic image;

FIGS. 11A and 11B are electron micrographs of a surface of soda glass processed by the method (Example 2) of the present invention. FIG. 11A is a planar image, and FIG. 11B is a stereoscopic image;

FIGS. 12A and 12B are electron micrographs of a surface of an unprocessed test piece (aluminum alloy: a product with hairline pattern). FIG. 12A is a planar image, and FIG. 12B is a stereoscopic image;

FIGS. 13A and 13B are electron micrographs of a surface of aluminum alloy processed by the method (Example 3) of the present invention. FIG. 13A is a planar image, and FIG. 13B is a stereoscopic image;

FIGS. 14A and 14B are electron micrographs of a surface of aluminum alloy processed by known blasting (Comparative Example 2: ejection pressure is 0.2 MPa). FIG. 14A is a planar image, and FIG. 14B is a stereoscopic image;

FIGS. 15A and 15B are electron micrographs of a surface of aluminum alloy processed by known blasting (Comparative Example 3: ejection pressure is 0.4 MPa). FIG. 15A is a planar image, and FIG. 15B is a stereoscopic image;

FIGS. 16A and 16B are electron micrographs of a surface of aluminum alloy processed by the method (Example 4) of the present invention. FIG. 16A is a planar image, and FIG. 16B is a stereoscopic image;

FIGS. 17A and 17B are electron micrographs of a surface of aluminum alloy processed by the method (Example 5) of the present invention. FIG. 17A is a planar image, and FIG. 17B is a stereoscopic image; and

FIG. 18 is an explanatory diagram schematically showing a situation in which cutting is being performed by known blasting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments according to the present invention will now be described with reference to the attached drawings.

Blast Nozzle

In FIG. 1, reference numeral 1 denotes a blast nozzle for use in a polishing method of the present invention. The blast nozzle 1 is intended to be attached to a known blasting apparatus (not shown) comprising a compressed gas supply source and an abrasive supply source, thereby making the polishing method of the present invention feasible.

The blast nozzle 1 comprises an accelerated flow generation nozzle 10 and an abrasive introduction path 20. The accelerated flow generation nozzle 10 is made to communicate with a compressed gas supply source provided in an unillustrated blasting apparatus and ejects a compressed gas which is introduced as an ejection fluid P1 from the compressed gas supply source, to a surface of a workpiece W to generate an accelerated flow S flowing along the surface of the workpiece W. The abrasive introduction path 20 introduces abrasive 30 from an unillustrated abrasive supply source (e.g., an abrasive tank), and merges the abrasive 30 with the accelerated flow S. An opening 21 of the abrasive introduction path 20 is arranged to face the surface of the workpiece W at the position of generation of the aforementioned accelerated flow S. Thus, the abrasive introduced into the abrasive introduction path 20 can be merged with the accelerated flow S and made to slide along the surface of the workpiece W.

In the illustrated embodiment, the accelerated flow generation nozzle 10 is formed as a cylindrical nozzle, and the abrasive introduction path 20 is formed into an approximately cylindrical shape having an inner diameter larger than the outer diameter of the accelerated flow generation nozzle 10. Further, part of the accelerated flow generation nozzle 10 on the tip side is arranged concentrically in the abrasive introduction path 20. Thus, the opening 21 of the abrasive introduction path 20 is formed around an ejection orifice 11 to surround the entire circumference of the ejection orifice 11 along the outer periphery thereof (see FIG. 2).

However, the shapes and arrangement of the accelerated flow generation nozzle 10 and the abrasive introduction path 20 are not restricted to the embodiment shown in FIGS. 1 to 3. For example, the abrasive introduction path 20 formed into a cylindrical shape in the illustrated example may be formed into the form of a rectangular tube or the like. Moreover, as shown in FIGS. 4A and 4B, a configuration may be employed in which the ejection orifice 11 of the accelerated flow generation nozzle 10 is formed into the form of a slit, and in which the opening 21 of the abrasive introduction path 20 is provided parallel to the ejection orifice 11 of the accelerated flow generation nozzle 10 formed into the form of a slit. Furthermore, as shown in FIGS. 5A and 5B, the opening 21 of the abrasive introduction path 20 may be arranged on each side of the ejection orifice 11 of the accelerated flow generation nozzle 10 (see FIG. 5B). Thus, various design modifications can be made as long as the opening 21 is pointed at the accelerated flow S generated by the accelerated flow generation nozzle 10, thereby abrasive can be merged with the accelerated flow S by providing the opening 21 of the abrasive introduction path 20.

The arrangement of the accelerated flow generation nozzle 10 and the abrasive introduction path 20 is determined such that the aforementioned ejection orifice 11 of the accelerated flow generation nozzle 10 is arranged to protrude from the opening 21 of the abrasive introduction path 20 in an ejection direction by a small protruding length (δ2 in FIG. 3).

The protruding length δ2 at a tip portion of the accelerated flow generation nozzle 10 is preferably 1.0 to 3.0 mm. In the illustrated embodiment, the protruding length δ2 is set to 1.0 mm so that the gap between the opening 21 of the abrasive introduction path 20 and the surface of the workpiece W becomes larger than the gap δ1 between the ejection orifice 11 of the accelerated flow generation nozzle 10 and the surface of the workpiece W when the ejection orifice 11 of the accelerated flow generation nozzle 10 is arranged to be pointed at the surface of the workpiece.

The introduction of the abrasive 30 into the aforementioned abrasive introduction path 20 may be performed by, for example, allowing abrasive to fall under gravity from an abrasive tank (not shown) arranged at a higher position than the abrasive introduction path 20. In this embodiment, however, the internal space of the aforementioned abrasive introduction path 20 is made to communicate with an abrasive tank (not shown) pressurized by a carrier fluid P2 which is a compressed gas, as in the case of an abrasive tank of a direct-pressure blasting apparatus. Thus, the abrasive 30 carried as a mixture fluid with the carrier fluid P2 can be introduced into the internal space of the abrasive introduction path 20 and merged with the accelerated flow S through the aforementioned opening 21.

To make such carrying of the abrasive 30 possible, in the embodiment shown in FIG. 1, an abrasive nozzle 24 is attached to a tip of an abrasive hose 25 communicating with the unillustrated abrasive tank to control the amount of abrasive carried. Further, a tip of the abrasive nozzle 24 is inserted into a connecting pipe 23 communicating with the internal space of the abrasive introduction path 20 so that the abrasive 30 can be introduced into the abrasive introduction path 20 together with the carrier fluid P2.

Polishing Method

As described previously, the compressed gas supply source of the unillustrated blasting apparatus is made to communicate with the accelerated flow generation nozzle 10 of the blast nozzle 1 configured as described above. A compressed gas at 0.1 to 0.7 MPa is introduced as the aforementioned ejection fluid P1 into the accelerated flow generation nozzle 10.

Moreover, the abrasive supply source of the unillustrated blasting apparatus is made to communicate with the abrasive introduction path 20 so that the abrasive 30 can be introduced into the abrasive introduction path 20. Here, in the case where the carrying of the abrasive 30 is performed by mixing the abrasive 30 with the aforementioned carrier fluid P2, the pressure of the carrier fluid P2 is set to a pressure lower than the pressure of the ejection fluid P1, preferably two-thirds or less of the pressure of the ejection fluid P1.

The kinds of an ejection fluid introduced into the accelerated flow generation nozzle 10 and a carrier fluid for use in carrying the abrasive 30 are not particularly restricted as long as the ejection fluid and the carrier fluid are compressed gases. In this embodiment, compressed air which is generally used in blasting was used.

However, various compressed gases can be used in accordance with processing conditions. For example, in the case where abrasive to be used is of a particle diameter or a material which creates a risk of dust fire, compressed inert gas is used.

As described above, the blast nozzle 1 is made to communicate with each of the compressed gas supply source and the abrasive supply source of the blasting apparatus, and the ejection fluid is ejected from the ejection orifice 11 of the accelerated flow generation nozzle 10 as shown in FIG. 3.

The gap δ1 between the tip of the accelerated flow generation nozzle 10 and the surface of the workpiece W is adjusted to a relatively narrow gap, preferably a gap of approximately 0.5 to 3.0 mm (in this embodiment, the gap δ1 is 1.0 mm) so that when the ejection fluid ejected from the ejection orifice 11 collides against the surface of the workpiece W and passes through the gap 61 between the nozzle tip and the surface of the workpiece W, the ejection fluid ejected from the ejection orifice 11 can change the direction thereof to generate the accelerated flow S along the surface of the workpiece W.

Moreover, to generate such an accelerated flow S with stability, the tip portion of the accelerated flow generation nozzle 10 is preferably formed to have a diameter φ (see FIG. 3) approximately 1.4 to 2 times the diameter of the ejection orifice 11. In this embodiment, as one example, the diameter of the ejection orifice 11 was set to 3 mm, and the diameter φ of the tip portion of the accelerated flow generation nozzle 10 was set to 5 mm.

Thus, when the ejection fluid P1 starts to be introduced into the accelerated flow generation nozzle 10 and the abrasive 30 is introduced into the abrasive introduction path 20 solely or as a mixture fluid with the carrier fluid P2, the ejection fluid P1 ejected from the ejection orifice 11 of the accelerated flow generation nozzle 10 is introduced into the gap δ1 between the accelerated flow generation nozzle 10 and the surface of the workpiece W to change the direction thereof, and is diffused in all directions around the accelerated flow generation nozzle 10, thus becoming the accelerated flow S flowing along the surface of the workpiece W.

Then, during the passage of the accelerated flow S through the gap between the opening 21 of the abrasive introduction path 20 and the surface of the workpiece, the abrasive 30 from the abrasive introduction path 20 is merged with the accelerated flow S. Thus, the abrasive 30 joins the accelerated flow S to slide along the surface of the workpiece.

As described previously, the ejection fluid P1 at a relatively high pressure, i.e., 0.1 to 0.7 MPa (in the embodiment, 0.3 MPa) introduced into the accelerated flow generation nozzle 10 passes through the relatively narrow gap δ1 of 0.5 to 3 mm (in the embodiment, 1.0 mm) formed between the tip of the accelerated flow generation nozzle 10 and the workpiece W, thus generating the accelerated flow S at a relatively high speed along the surface of the workpiece. The accelerated flow S functions like an air curtain covering the surface of the workpiece W.

Accordingly, even in the case where the introduction of the abrasive into the abrasive introduction path 20 is performed using the carrier fluid P2 which is a compressed gas, it becomes possible to prevent the abrasive 30 from colliding against the surface of the workpiece W in the vertical direction and therefore prevent the abrasive 30 from exerting cutting force on the surface of the workpiece W in the vertical direction.

In particular, in the case where the pressure of the carrier fluid P2 is set to a pressure lower than the pressure of the ejection fluid P1, preferably two-thirds or less of the pressure of the ejection fluid P1, it is possible to greatly inhibit the abrasive 30 from exerting cutting force on the surface of the workpiece W in the vertical direction.

Moreover, by introducing the abrasive in this way using the carrier fluid P2 which is a compressed gas, a carrier gas is ejected from the opening 21 of the abrasive introduction path 20 such that the accelerated flow S is pressed against the surface of the workpiece W. Accordingly, the accelerated flow S can be prevented from being separated from the surface of the workpiece W, and can be moved along the surface of the workpiece W over a longer distance.

As a result, unlike conventional general blasting methods in which abrasive exerts cutting force on the surface of the workpiece W in the direction perpendicular thereto, in the polishing method of the present invention, horizontal cutting force can be exerted on the surface of the workpiece W by making the abrasive 30 slide along the surface of the workpiece W. This makes it possible to gradually perform polishing and removal from peaks of irregularities originally existing on the surface of the workpiece as shown in FIG. 6.

In the polishing method of the present invention, the above-described function of cutting does not scrape off a surface of a workpiece in a depth direction more than necessary. Moreover, since soft polishing is performed only with the energy of a compressed gas, a deep scratch formed by polishing can be prevented from being newly made in an polishing step.

Moreover, in the polishing method of the present invention, unlike lapping, polishing, and the like, nothing but abrasive touches a workpiece. Accordingly, excess stresses are less prone to occur in the workpiece during and after polishing. Thus, the polishing method of the present invention has the effect of preventing the occurrence of strains and the like. Also, in comparison to conventional general blasting methods, since abrasive is inhibited from colliding against the surface of the workpiece in the vertical direction, stresses and strains are less prone to occur similarly.

Next, a description will be made of processing test examples as examples in which various test pieces are processed by the polishing method of the present invention.

It should be noted that a blast nozzle used in the examples which will be described below has a structure similar to that described with reference to FIG. 1. The diameter of the ejection orifice 11 of the accelerated flow generation nozzle 10 was 3 mm, the diameter (φ) of the nozzle tip portion was 5 mm, the diameter of the opening 21 of the abrasive introduction path 20 was 20 mm, and the protruding length δ2 at the tip portion of the accelerated flow generation nozzle 10 was 1.0 mm.

Moreover, in each of the examples, the gap δ1 between the tip of the accelerated flow generation nozzle and a surface of a workpiece W was 1.0 mm. Further, in each of the examples and comparative examples, a plate body having a width of 90 mm and a length of 90 mm was used as a test piece, and half (45 mm×90 mm) of the plate body was observed.

Processing Examples using Glass Plate Comparison with General Blasting

Object of Comparative Processing

To confirm differences in the behavior of abrasive at surfaces of test pieces between the polishing method of the present invention (Example 1) and conventional general blasting (Comparative Example 1) in which the abrasive is ejected together with a compressed gas, by performing each of the two processing methods on a surface (minor surface) of a test piece without irregularities and observing changes in the surfaces of the test pieces after processing.

Processing Conditions Example 1

Test piece: soda glass (minor surface)

Abrasive: High purity alumina abrasive “FUJIRANDOM WA #220” (average particle diameter: 53 to 45 μm) manufactured by FUJI MANUFACTURING CO., LTD.

Supply pressure: Accelerated flow generation nozzle; 0.3 MPa (compressed air)

Abrasive supply nozzle; 0.1 MPa (compressed air)+abrasive

Processing time: 13 minutes (processing time for the observe area of 45 mm×90 mm; the same applies hereinafter)

Comparative Example 1

Test Piece: Soda glass (Minor surface)

Abrasive: High purity alumina abrasive “FUJIRANDOM WA #600” (Average particle diameter: 20.0±1.5 μm) manufactured by FUJI MANUFACTURING CO., LTD.

Ejection method: Abrasive is ejected to the surface of the test piece in the vertical direction together with a compressed air at 0.4 MPa

Processing time: 1 minute

Results of Processing

FIGS. 8A and 8B show the state of a surface of an unprocessed test piece (workpiece used in Example 1). FIGS. 9A and 9B show the state of the surface of the test piece of Example 1 after processing. FIGS. 10A and 10B show the state of the surface of the test piece of Comparative Example 1 after processing.

Moreover, the surface roughness of each test piece is shown in Table 1 below.

TABLE 1 Data on Surface Roughness of Glass Test Pieces (Example 1, Comparative Example 1) Unprocessed* Example 1 Comparative Example 1 Ra (μm) 0.056 0.266 1.094 Ry (μm) 0.400 5.870 16.700 Rz (μm) 0.242 4.864 13.872 tp (50%) 41.3 98.7 85.8 RMS (μm) 0.068 0.395 1.398 *The “unprocessed” test piece was the one used in Example 1.

Here, of the above-described parameters of roughness, each of Ra (arithmetical mean roughness), Ry (maximum peak), Rz (ten-point mean roughness), and tp (load length rate) is compliant with JIS (Japanese Industrial Standard) (JISB 0601-1994) (the same applies hereinafter).

Moreover, RMS is “root mean square roughness.”. This value is found as the root of the mean of the squares of deviations of a measured profile from a mean line based on a roughness profile (see FIG. 7: the same applies hereinafter).

Discussion Based on Results of Processing

As can be seen from the comparison between FIGS. 8A, 8B and FIGS. 10A, 10B, the surface of the test piece which had been a mirror surface before processing (FIGS. 8A and 8B) changed to an irregular surface having sharp peaks and valleys after the processing of Comparative Example 1 (see FIG. 10B).

Moreover, in the processing method of Comparative Example 1, though abrasive with a small particle diameter (accordingly, in general, abrasive with low surface roughening function) was used compared to that of the processing method of Example 1, it was confirmed that each parameter of surface roughness after processing greatly increased compared to that of the processing method of Example 1.

This proves that in a known blasting method in which abrasive is collided with a surface of a test piece together with a compressed gas as in Comparative Example 1, the collided abrasive exerts the function of cutting the surface of the test piece in the vertical (depth) direction.

On the other hand, in the case where the processing of Example 1 was performed, though the surface of the unprocessed test piece which had been a minor surface was scraped to form irregularities, it can be confirmed that peaks and valleys of these irregularities are not sharp unlike those of Comparative Example 1 but relatively gentle (see FIG. 9B).

Moreover, in Example 1, though abrasive with a large particle diameter, i.e., abrasive having high surface roughening effect was used compared to that of Comparative Example 1, the increase in each parameter of roughness was small (difference in height of the formed irregularities was small) compared to that of Comparative Example 1 on the surface of the test piece after the processing of Example 1. This proves that the processing of Example 1 can greatly inhibit cutting force from exerting on the surface of the test piece in the direction perpendicular thereto.

The above-described results prove that there are significant differences in the behavior of the abrasive at the surfaces of the test pieces between the two processings of Example 1 and Comparative Example 1. As described with reference to FIG. 18, in the conventional general blasting method, abrasive cuts a surface of a workpiece in the depth direction using the collision energy. On the other hand, it can be seen that as described with reference to FIG. 6, the polishing method (Example 1) of the present invention exerts horizontal cutting force on the surface of the test piece by making abrasive slide along the surface of the workpiece.

Moreover, it can be seen that cutting principles of the above-described method (Example 1) of the present invention can prevent damage to a surface of a workpiece caused by the collision of abrasive (abrasive grains) such as in known blasting, and enables the work of thinly scraping off a surface portion of the workpiece, which has been difficult in conventional blasting.

Example 2 (Processing for Improving Surface Roughness) Object of Processing

To confirm that the surface roughness of a test piece can be improved (surface of a test piece can be planarized) by applying the polishing method of the present invention to a glass test piece having irregularities on a surface thereof.

Processing Conditions

Test Piece: Soda Glass (after the Processing of Comparative Example 1)

Abrasive: High purity alumina abrasive “FUJIRANDOM WA #1000” (Average particle diameter: 11.5±1.0 μm) manufactured By FUJI MANUFACTURING CO., LTD.

Supply Pressure: Accelerated flow generation nozzle; 0.3 MPa (compressed air)

Abrasive supply nozzle; 0.1 MPa (compressed air)+abrasive

Processing time: 13 minutes

Results of Processing

FIGS. 11A and 11B show the state of the surface of the test piece after the processing of Example 2 (with regard to the state of the surface before processing, see FIGS. 10A and 10B).

Moreover, the surface roughness of each test piece is shown in Table 2 below.

TABLE 2 Data on Surface Roughness of Glass Test Pieces (Example 2) Unprocessed (Comparative Example 1) Example 2 Ra (μm) 1.094 0.601 Ry (μm) 16.700 6.370 Rz (μm) 13.872 3.646 tp (50%) 85.8 95.5 RMS (μm) 1.398 0.751

Discussion Based on Results of Processing

From the above-described results, it was confirmed that the surface roughness of the test piece was improved (surface of the test piece was planarized) by the method (Example 2) of the present invention.

Moreover, as can be seen from the comparison between FIG. 10B and FIG. 11B, surface irregularities (see FIG. 10B) of the test piece which had had sharp peaks and valleys in an unprocessed state changed to a gentle shape of irregularities in which edges were removed, after the processing of the method (Example 2) of the present invention (see FIG. 11B).

Moreover, each of the values of parameters Ra, Ry, Rz, and RMS indicating surface roughness indicates that in the surface of the test piece after the processing of the present invention, the surface roughness was improved, i.e., the difference in height of irregularities decreased.

Also, of the parameters of roughness, the increase in the value of tp indicates that a cutting level of 50% moved to the valley side of original irregularities, accordingly, the heights of peaks were decreased compared to original irregularities. It can be seen that as described with reference to FIG. 6, polishing according to the method of the present invention exerts horizontal cutting force by the sliding of abrasive along the surface of the test piece, and is performed by cutting peaks of irregularities in a horizontal direction.

As described above, it was confirmed that the polishing method of the present invention can also be applied to the improvement (smoothing) of flatness of the surface of the workpiece, which was difficult in conventional general blasting.

Processing Examples using Aluminum Alloy

Example 3, Comparative Examples 2, 3 (Processing for Improving Surface Roughness) Object of Processing

To confirm that the surface roughness of a test piece can be improved by applying the polishing method of the present invention to the test piece having irregularities (hairline pattern) produced on a surface thereof, and to make a comparison with a processed state in the case where known blasting is performed on a test piece having similar irregularities (hairline pattern) formed thereon and confirm differences in the behavior exhibited by the abrasive at the surfaces of the test pieces for the two processing methods.

Processing (Test) Conditions Example 3

Test piece: Aluminum alloy product (A5052P; Alloy No. JIS H4000 (Al—Mg Alloy), P: Plate; Plate material) with hairline pattern

Abrasive: High purity alumina abrasive “FUJIRANDOM WA #1000” (Average particle diameter: 11.5±1.0 μm) manufactured by FUJI MANUFACTURING CO., LTD.

Supply pressure: Accelerated flow generation nozzle; 0.3 MPa (compressed air)

Abrasive supply nozzle; 0.1 MPa (compressed air)+abrasive

Processing time: 13 minutes

Comparative Example 2

Test piece: Aluminum alloy product (A5052P) with hairline pattern

Abrasive: High purity alumina abrasive “FUJIRANDOM WA #1000” (Average particle diameter: 11.5±1.0 μm) manufactured by FUJI MANUFACTURING CO., LTD.

Ejection method: Abrasive is ejected to the surface of the test piece in the vertical direction together with a compressed air at 0.2 MPa (distance between the nozzle and the test piece is 150 mm)

Processing time: 30 seconds

Comparative Example 3

Test piece: Aluminum alloy product (A5052P) with hairline pattern

Abrasive: High purity alumina abrasive “FUJIRANDOM WA #1000” (Average particle diameter: 11.5±1.0 μm) manufactured by FUJI MANUFACTURING CO., LTD.

Ejection method: Abrasive is ejected to the surface of the test piece in the vertical direction together with a compressed air at 0.4 MPa (Distance between the nozzle and the test piece: 150 mm)

Processing time: 30 seconds

Results of Processing

FIGS. 12A and 12B show the state of a surface of an unprocessed test piece (workpiece of Example 3). FIGS. 13A and 13B show the state of a surface of the test piece after the processing of the method (Example 3) of the present invention. FIGS. 14A and 14B show the test piece processed by conventional general blasting (Comparative Example 2) in which ejection pressure was 0.2 MPa. FIGS. 15A and 15B show the test piece processed by conventional general blasting (Comparative Example 3) in which ejection pressure was 0.4 MPa.

Moreover, the surface roughness of each test piece is shown in Table 3 below.

TABLE 3 Data on Surface Roughness of Glass Test Pieces (Example 3, Comparative Examples 2 and 3) Parameter Unprocessed* Example 3 Comp. Ex. 2 Comp. Ex. 3 Ra (μm) 0.247 0.133 0.279 0.412 Ry (μm) 2.540 2.380 4.040 6.310 Rz (μm) 2.042 1.818 2.868 5.238 tp (50%) 78.2 63.8 80.6 36.8 RMS (μm) 0.305 0.170 0.345 0.518 *The “unprocessed” test piece was the one used in Example 3.

Discussion Based on Results of Processing

From the above-described results, it was confirmed that in the polishing method (Example 3) of the present invention, the surface roughness of an unprocessed test piece was improved, and the method of the present invention can also perform favorable polishing on materials such as aluminum which may exhibit plastic deformation due to the collision of abrasive, without producing a satin finished surface and the like.

Moreover, as can be seen from the comparison between FIGS. 12A, 12B and FIGS. 13A, 13B, hairline pattern (recessed grooves and protrusions extending across the width of the test piece: see FIGS. 12A and 12B) which clearly showed on the surface of the unprocessed test piece completely disappeared (FIGS. 13A and 13B) after the processing (Example 3) of the present invention was performed.

On the other hand, in conventional general blasting, in the case where processing was performed with an ejection pressure of 0.2 MPa to such an extent that the surface roughness (Ra as one example) of the test piece does not greatly change (deteriorate) (Comparative Example 2), the evidence of hairline pattern was clearly confirmed (see FIGS. 14A and 14B), and the surface roughness was not improved but deteriorated (see Table 3).

Moreover, in the conventional general blasting, in the case where the ejection pressure was set to 0.4 MPa to further increase the degree of processing (Comparative Example 3), the existence of hairline pattern was unsharp compared to that of Comparative Example 2 as shown in FIGS. 15A and 15B. However, in a stereoscopic image shown in FIG. 15B, the observation of the shapes of two opposite sides in the longitudinal direction revealed the coincidence of appearance patterns of irregularities. It can be seen that the shape of irregularities corresponding to peaks and valleys in original hairline pattern is still maintained.

Also, by increasing the degree of processing in this way, the value of roughness greatly increased even compared to the test piece of Comparative Example 2 as well as the unprocessed test piece. Thus, it was confirmed that the surface roughness was further deteriorated rather than being improved.

The above-described results of processing prove that in conventional general blasting, cutting in the depth direction was performed on the entire surface of the test piece with morphological characteristics of original surface irregularities maintained as described with reference to FIG. 18. As a result, in the case where a test piece having hairline pattern formed thereon is processed, even if the amount of cutting had been increased, the scratch lines of the hairline pattern or the evidence thereof could not have been completely removed.

On the other hand, in the processing method (Example 3) of the present invention, as is apparent from the fact that hairline pattern originally existing on the surface of the unprocessed test piece completely disappeared, it is thought that morphological characteristics of original irregularities was efficiently caused to disappear by minimal cutting without increasing the amount of cutting in the depth direction by making abrasive slide along the surface of the workpiece to cut and remove peaks of irregularities as described with reference to FIG. 6.

From the above-described characteristics, it is thought that the polishing method of the present invention can be favorably applied to work such as the improvement of flatness, the removal of tool marks made by various machine parts and the like, and the removal of a coating formed on a surface without causing surface roughening, which cannot be performed by conventional general blasting methods.

It should be noted that the value 0.133 μm of Ra of surface roughness after the processing of Example 3 indicates surface roughness comparable with that obtained when processing is performed by conventional general blasting using fine abrasive of a grit number (approximately #3000) approximately three times as large as that of Example 3.

In general, with decreasing particle diameter, the price of abrasive increases, and the degree of difficulty of handling the abrasive increases due to agglomeration caused by the coupling between particles, the pollution of a work environment caused by scattered or suspended particles, the risk of a dust fire depending on the material, and the like. It is understood that in the method of the present invention, even if abrasive with a large particle diameter, i.e., inexpensive and easy-to-handle abrasive, is used compared to that of conventional general blasting, comparative or better effects can be obtained.

Examples 3 to 5 (Confirmation of Influence of Changes in Processing Conditions) Object of Processing

To confirm the influence of changes in the particle diameter of abrasive to be used and abrasive supply pressure (pressure of the carrier fluid P2 in FIG. 1) on processed states.

Processing Method

Three (3) test pieces, each made of an aluminum alloy plate (A5052P) with hairline pattern, were processed by the method of the present invention under processing conditions shown in Table 4 below, respectively.

TABLE 4 Processing Conditions (Examples 3 to 5) Abrasive (aforementioned “Fujirandom”) Supply Pressure Average Particle Accelerated Abrasive Processing Example Material Grit No. diameter (μm) Flow Supply Time (Min.) Example 3 WA #1000 11.5 ± 1.0  0.3 MPa 0.1 MPa 13 Example 4 (Alumina) #3000 4.0 ± 0.5 0.3 MPa 0.2 MPa 10 Example 5 #220 53 − 45 0.3 MPa 0.1 MPa 13

Results of Processing

FIGS. 16A and 16B show the state of a surface of the test piece after the processing of Example 4. FIGS. 17A and 17B show the state of a surface of the test piece after the processing of Example 5.

For the state of a surface of an unprocessed test piece (workpiece of Example 3), see FIGS. 12A and 12B. For the state of a surface of the test piece after processing of Example 3, see FIGS. 13A and 13B.

Moreover, the surface roughness of each test piece is shown in Table 5 below.

TABLE 5 Data on Surface Roughness of Aluminum Test Pieces (Examples 3 to 5) Parameter Unprocessed* Example 3 Example 4 Example 5 Ra (μm) 0.247 0.133 0.182 0.410 Ry (μm) 2.540 2.380 3.580 7.940 Rz (μm) 2.042 1.818 1.886 5.234 tp (50%) 78.2 63.8 43.2 90.7 RMS (μm) 0.305 0.170 0.235 0.528 *The “unprocessed” test piece was the one used in Example 3.

Discussion Based on Results of Processing

From the above-described results, it was confirmed that hairline pattern was removed for each of the test pieces processed under the conditions of Examples 3 to 5 (see FIGS. 13A, 13B, 16A, 16B, 17A, and 17B).

In the case where abrasive exerts cutting force on a surface of a test piece in the depth direction as in conventional general blasting (Comparative Examples 2 and 3), hairline pattern cannot be completely removed. In view of this, each of the processings of Examples 3 to 5 in which hairline pattern disappeared seem to be capable of exerting horizontal cutting force on a surface of a test piece by making abrasive slide along the surface of the workpiece, irrespective of differences in the particle diameter of abrasive used.

Moreover, in Examples 3 and 5, the pressure of the carrier fluid P2 for use in carrying abrasive was set to 0.1 MPa. On the other hand, in Example 4, the pressure of the carrier fluid P2 for use in carrying abrasive was doubled to 0.2 MPa, i.e., increased to two-thirds of the pressure of the ejection fluid P1. It was confirmed that despite such a pressure increase, cutting in the vertical direction performed on a surface of a workpiece was inhibited.

Instead of conventional general blasting and known polishing methods, e.g., polishing using polishing paper or polishing cloth, lapping, buffing, ultrasonic polishing, and the like, the above-described polishing method using a nozzle having the nozzle structure for a blasting apparatus of the present invention can be utilized in various fields in which the foregoing methods have been performed.

In particular, the polishing method of the present invention is performed by exerting horizontal cutting force while making abrasive slide along a surface of a workpiece to inhibit vertical cutting force acting on the surface of the workpiece from occurring. Accordingly, damage to the workpiece can be reduced as much as possible, and polishing in which a surface portion is thinly scraped off can be performed by reducing the amount of cutting in the depth direction. Thus, the polishing method of the present invention is expected to be used particularly in the following fields.

Pretreatment before Lapping

The method of the present invention can be utilized to improve the surface roughness of a workpiece as pretreatment before lapping. In particular, since the method of the present invention causes less damage to the workpiece as described previously, the method of the present invention is suitable for use in pretreatment before, for example, polishing of a wafer (silicon, quartz, sapphire, or the like). Also, since the method of the present invention has the effect of greatly improving surface roughness, it is expected that the labor of lapping to be performed later can be greatly reduced.

Thin Film Removal and the Like

In the method of the present invention, the sliding of abrasive along a surface of a workpiece enables cutting near the surface without increasing the amount of cutting in the depth direction. Accordingly, in an operation such as the removal of a thin film formed on a surface of a silicon wafer, the thin film can be removed without cutting a base material deeper than necessary.

In particular, even a thin film of a different material formed on the thin film can be removed by one step of the method of the present invention. This eliminates the necessity of complicated work including a change of chemical solutions according to the material of a coating such as in the case of removal by chemical etching.

Pretreatment (Surface Activation) before Formation of Laminated film

Further, in the method of the present invention, a surface of a workpiece can be very thinly scraped off using abrasive sliding along the surface of the workpiece. Accordingly, for example, by performing the surface treatment of the present invention on a surface of a base material before the formation of a laminated film by sputtering, various kinds of deposition, and the like, the work of removing an oxidation coating and the like existing on the surface and exposing an active surface is thought to be capable of being performed without greatly reducing the flatness of the base material.

Thus, it is expected that the bonding strength between the base material and the laminated film can be improved by performing the polishing method of the present invention as pretreatment before the laminated film is formed by sputtering and various kinds of deposition.

Removal of Scratches and Tool Marks

It should be noted that since hairline pattern formed on a test piece can be removed by the method of the present invention as described previously, the method of the present invention can also be favorably utilized in the removal of scratches produced on surfaces of dies, molds, and various machining parts, tool marks produced as traces of contact with bits, and the like.

Thus the broadest claims that follow are not directed to a machine that is configure in a specific way. Instead, said broadest claims are intended to protect the heart or essence of this breakthrough invention. This invention is clearly new and useful. Moreover, it was not obvious to those of ordinary skill in the art at the time it was made, in view of the prior art when considered as a whole.

Moreover, in view of the revolutionary nature of this invention, it is clearly a pioneering invention. As such, the claims that follow are entitled to very broad interpretation so as to protect the heart of this invention, as a matter of law.

It will thus be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Now that the invention has been described; 

1. A polishing method by blasting, comprising the steps of: introducing a compressed gas containing no abrasive as an ejection fluid into an accelerated flow generation nozzle arranged to be pointed at a surface of a workpiece and ejecting the compressed gas to generate an accelerated flow along the surface of the workpiece, and introducing abrasive into an abrasive introduction path opening toward the surface of the workpiece at an area where the accelerated flow is generated to merge the abrasive with the accelerated flow and make the abrasive slide along the surface of the workpiece.
 2. The polishing method by blasting according to claim 1, wherein the abrasive is mixed with a carrier fluid which is a compressed gas at a pressure lower than the pressure of the ejection fluid introduced into the accelerated flow generation nozzle, to be introduced into the abrasive introduction path.
 3. The polishing method by blasting according to claim 2, wherein a pressure of the carrier fluid is set to two-thirds or less of that of the ejection fluid.
 4. The polishing method by blasting according to claim 1, wherein a gap between an opening of the abrasive introduction path and the surface of the workpiece is larger than a gap between an ejection orifice of the accelerated flow generation nozzle and the surface of the workpiece.
 5. A nozzle structure for a blasting apparatus, comprising: an accelerated flow generation nozzle for ejecting a compressed gas containing no abrasive supplied as an ejection fluid from a compressed gas supply source toward a surface of a workpiece to generate an accelerated flow along the surface of the workpiece, and an abrasive introduction path opening toward the surface of the workpiece at an area where the accelerated flow is generated and having abrasive from an abrasive supply source supplied thereto.
 6. The nozzle structure for a blasting apparatus according to claim 5, wherein the abrasive introduction path is made to communicate with the abrasive supply source for supplying the abrasive as a mixture fluid with a carrier fluid which is a compressed gas.
 7. The nozzle structure for a blasting apparatus according to claim 5, wherein an end portion of the accelerated flow generation nozzle on the ejection orifice side is arranged in the abrasive introduction path.
 8. The nozzle structure for a blasting apparatus according to claim 5, wherein an ejection orifice of the accelerated flow generation nozzle is formed into a form of a slit, and an opening of the abrasive introduction path is arranged parallel to the ejection orifice.
 9. The nozzle structure for a blasting apparatus according to claim 8, wherein the opening of the abrasive introduction path is arranged on each of opposite sides of the ejection orifice of the accelerated flow generation nozzle.
 10. The nozzle structure for a blasting apparatus according to claim 5, wherein a gap between an ejection orifice of the accelerated flow generation nozzle and the surface of the workpiece is set to 0.5 to 3.0 mm, and a gap between an opening of the abrasive introduction path and the surface of the workpiece is formed to be wider than the gap between the ejection orifice of the accelerated flow generation nozzle and the surface of the workpiece by 1.0 to 3.0 mm.
 11. The nozzle structure for a blasting apparatus according to claim 10, wherein the ejection orifice of the accelerated flow generation nozzle protrudes from the opening of the abrasive introduction path in an ejection direction by 1.0 to 3.0 mm. 